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# How many photons will a molecule of water have when it turns into energy?

Tue 10 Feb, 2015 11:33 am

Who knows this question about science?
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Type: Question • Score: 2 • Views: 970 • Replies: 7
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Frank Apisa

2
Tue 10 Feb, 2015 12:10 pm
@oristarA,
oristarA wrote:

Who knows this question about science?

I know the question, Oristar. (It's right there!)

Not sure I understand it.

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contrex

1
Tue 10 Feb, 2015 12:39 pm
By what process could one convert water into energy?
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Tryagain

2
Tue 10 Feb, 2015 02:05 pm
1) calculate total energy to needed to melt ice
2) calculate energy per photon
3) calculate number of photons...

like this...

*** 1 ***
assuming all the photons are absorbed....
heat required to melt ice = energy of all the photons.
4.0x10^2 g x 334 J/g = energy of photons.
1.34x10^5 J = energy of photons.

*** 2 ***
then...for a single photon...
E = hc/L = 6.626x10^-34 J s x (3.00x10^8 m/s) / (660 nm x 1m/10^9nm) = 3.01x10^-19 J

ie... 3.01x10^-19 J/photon.

*** 3 ***
1.34x10^5 J x (1 photon / 3.01x10^-19J) = 4.4x10^23 photons

Therefore:

4.0x10^2 g x (1 mole / 18.0g) x (6.022x10^23 molecules / mole) = 1.34x10^25 molecules of water

then...
1.34x10^25 molecules of water / 4.4x10^23 photons = 30 molecules of water per photon.

By what process could one convert water into energy?”

Someday someone will invent a mill, steam engine or turbine.

contrex

2
Tue 10 Feb, 2015 02:16 pm
@Tryagain,
Tryagain wrote:
By what process could one convert water into energy?”

Someday someone will invent a mill, steam engine or turbine.

Mills, steam engines and turbines do not convert water into energy.
oristarA

0
Tue 10 Feb, 2015 11:11 pm
@contrex,
contrex wrote:

Tryagain wrote:
By what process could one convert water into energy?”

Someday someone will invent a mill, steam engine or turbine.

Mills, steam engines and turbines do not convert water into energy.

Yes you are correct that such converting would never happen.

To convert a molecule of water into photons, simply let it meet its antimolecule and both will be annihilated into photons (energy). Making antimatter is a frontier in particle physics.
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oristarA

0
Tue 10 Feb, 2015 11:19 pm
@Tryagain,
Tryagain wrote:

1) calculate total energy to needed to melt ice
2) calculate energy per photon
3) calculate number of photons...

But 1) is wrong. The correct calculation is to use Einstein's mass-energy equation: E = mc^2. The m in the equation refers to the mass of a molecule of water, c is speed of light and E is the total energy of the molecule.

Since your premise 1) is not correct, you got an erroneous result of the calculation.

I haven't found the data about the mass of a molecule of water.
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raprap

1
Wed 11 Feb, 2015 12:32 am
@oristarA,
Ignoring the second law of thermodynamics, equate the energy of fusion of water to hu, as in E=hu (Planc's law) and count your photons. Of course you'll have to define the frequency)

Rap
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